"simultaneous conflicting feelings," 1924 (1912 as ambivalency), from German Ambivalenz, coined 1910 by Swiss psychologist Eugen Bleuler (1857-1939) on model of German Equivalenz "equivalence," etc., from Latin ambi- "both, on both sides" (see ambi-) + valentia "strength," abstract noun from present participle of valere "be strong" (from PIE root *wal- "to be strong"). A psychological term that by 1929 had taken on a broader literary and general sense.